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Honda M/Cycle Cb 750 '95 Query

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A friend laid his bike over briefly (properly supported where necessary in garage) to inspect an exhaust problem beneath the frame, and lost a small amount of oil from what is thought to be the gear-change reservoir. Despite googling and consulting manuals, there appears to be no info about this, ie, whether it is standard engine oil or other, and no obvious means provided to set the correct level. There is a black plastic screw cap which plugs the filler orifice.

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What is a gear change reservoir?

 

Any bike I’ve ever known has any gear change mechanism lubricated by engine oil in the crankcase/gearbox.

 

Is this a new thing?

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Older bikes did have a separate gearbox with EP 80 gear oil. The gear-trains on these more modern Hondas possibly run in the engine oil, however there (seems to be) a separate compartment housing the gearchange selector mechanisms and this, as far as I can ascertain, appears to be immersed in its own independant oil bath, and it's this that I need to clarify.

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I have never come across any motorcycle except maybe pre-unit Triumphs, which has a separate gearbox with its own oil.

 

If this is the case with your mate’s bike, the gear select mechanism will almost certainly be in gearbox oil as I can’t see Honda designing a bike with three different types of oil.

 

What was the oil that leaked out like? Engine oil is usually quite dark and smells quite sweet. Gearbox oil is usually either red, green or blue and STINKS!

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Posted (edited)

Not sure but going to compare in morning. BSA A65/50 unit construction had separate gear oil.

 

See exploded parts list:   https://www.bike-parts-honda.com/honda-motorcycle/750-MOTO/CB/1995/CB750F2S/Engine/GEARSHIFT-DRUM/13MW3M11/E__1700/1/1759

 

Case is (1), and plastic filler cap is (2). This is on opposite side of engine to the ordinary oil filler cap.

 

Nowhere in Honda manuals (as far as I can see) does it mention lubrication for above.

 

UPDATE:   it seems that it is engine oil, so it looks like the crankcase oil compartment extends from one side of the engine to the other. What is confusing is having (what appears to be) a 2nd plastic filler cap on the opposite side, giving the impression that there is a separate oil compartment.

Edited by carosio
update

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Sure it's not a blanking plug?

 

You can hotlink pictures now on the forum so maybe a couple of shots would demonstrate what you're talking about?

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3 hours ago, geared said:

Sure it's not a blanking plug?

 

You can hotlink pictures now on the forum so maybe a couple of shots would demonstrate what you're talking about?

how is this done please?

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I'll post a pic or link up shortly.

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Posted (edited)
47 minutes ago, Top Cats Hat said:

Crankcase breather? Dipstick?

No, dipstick is on oil filler cap at other side.

here is pic, it does actually say on the cap DO NOT OPEN, but people will and I initially thought that this area was where the spillage came from.zkMXvUE.jpg

Edited by carosio

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Has the engine been cleaned?

 

I’m seeing a lot of engine oil on the lower frame tube and the side stand fixing point but nothing around the mystery ‘filler cap’. There also appears to be an o-ring around it so I’d say that it was highly unlikely that cold unpressurised oil would leak from there.

 

I think that it has come out of some kind of breather pipe somewhere.

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You could be right on the breather pipe. There is no oil on the tubes, it's just how the flash has reflected off a section of the tubes that was re-sprayed. The leaked oil was noticed on the ground, none on the bike.

 

Just that it is a mystery of the purpose of the screw "filler cap".

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